1. Field of the Invention
This invention relates to a ball check valve for use in pipes handling fluids such as service water, medium water, sewage water, agricultural water, dirty water, plant effluent, miscellaneous effluents, oils and gases; and to a pumping apparatus using the ball check valve for the purpose of pumping such liquids and oils in a sewage tank, a manhole pumping station, a reservoir, etc.
2. Description of the Prior Art
The ball check valve of this kind comprises a ball formed by closely encompassing a metallic sphere with a coat of rubber or resin and built in a body, an inlet and an outlet inserted in the body, a ball seating part and a guide part adapted to guide a ball and disposed inside the body, and achieves the purpose of causing the ball, when a fluid is in normal flow, to be retracted to a position incapable of offering obstruction to the flow of the fluid and, when the fluid is stopped, to be moved under its own weight to a closing position.
This check valve is usable only in a vertical pipe having the secondary side thereof turned upward and is unusable in a pipe laid in a horizontal state. Particularly, the guide part which is disposed inside the body, being made of cast metal, does not always have a constant size and position and, therefore, is generally so positioned as to give the ball free room relative to its diameter. When this check valve is set in a horizontal state which emits no load, therefore, it cannot be effectively used in a horizontal pipe because the horizontal state possibly prevents the ball from contacting the seating part.
One of the inventors in this instance has already proposed an invention pertaining to this ball check valve in JP-A-10-231,941.
The invention of this prior patent publication contemplates preventing the ball from flowing through the outlet or inlet into the pipe by causing the minimum sizes of the inlet and the outlet of the body in the direction of diameter to be smaller than the diameter of the metallic sphere. Though the prior invention is intended to be used mainly in a vertical pipe, it additionally proposes a construction which, for the purpose of allowing application to a horizontal pipe as well as to a vertical pipe, is provided near the seating part with a projecting part capable of causing the ball to collide against the seating part when the fluid ceases normal flow and the ball consequently moves to the position for closing the valve.
According to the prior patent publication, since the horizontal pipe under discussion has the seating part thereof disposed perpendicularly to the center of the flow path, the ball is not easily set in position on the seating part during the absence of load. Particularly when a large reverse current occurs, though the ball is indeed seated, it possibly induces water hammer. Conversely, if the reverse current is unduly small, the ball will not be seated so effectively as to afford perfect closure of the flow path.
A ball check valve is adopted for various applications. When it is used for a pump system in a manhole, for example, the submersible pump is provided in the upper part thereof with two (or one) pumping functions and is operated to pump up the fluid stored in the manhole and control the amount of the stored fluid at a constant level. After the pump is stopped, the check valve is set in a closed state to prevent the fluid from flowing back.
Generally in this case, the pipe which interconnects the check valve and the pump is provided with an air vent valve besides the check valve so as to allow a constant flow of air through the pipe.
Particularly when the pump is stopped, the pressure of the water head on the secondary side pipe actuates the check valve and closes it. In this case, the check valve fails to function in the absence of a pressure difference between the primary side and the secondary side. Specifically, since the pumping system requires the pressure on the primary side to be duly small and necessitates extraction of the water in the primary side pipe by means of the pump, for example, it becomes necessary first of all to extract the air entrapped in the primary side pipe through the air vent valve.
Also, when the pump is actuated to start pumping the water, it is necessary to extract the air promptly through the air vent valve because the presence of air in the pipe results in degrading the capacity of the pump.
Thus, the pumping system is adapted to rely on the air vent valve to extract the air contained in the pipe interconnecting the check valve and the pump.
The desirability of integrating the air vent valve with the check valve instead of disposing the air vent valve independently of the check valve has been advocated. The proposed integration has not yet been realized because it possibly results in enlarging the check valve itself and altering the interfacial dimensions of the valves in question and deprives the valves of exchangeability with the conventional supplies by reason of size.
Particularly, the manhole pumping system which is designed for alternately actuating two parallel lines each formed of a series of pumping and reverse flow preventing parts cannot be applied to the conventional manhole because this system abounds in component elements including pipes and because the change in layout of the system incurs a very high cost.
Incidentally, when the ball check valve of this kind serves a submersible pump which is propelling dirty water containing pebbles of a general size in the approximate range of 5-10 mm, since the ball of the ball check valve is moved toward the guide side in concert with the dirty water entraining the pebbles, the possibility of the pebbles being nipped between the ball and the guiding part is undeniable. Consequently, the ball fails to land on the seating part of the valve box.
This situation is depicted in FIG. 22. With reference to the diagram, when a pebble 51 is engulfed into the gap between a ball 52 and a guiding part 53 in a valve box 54, the pebble 51 is suffered to restrain the movability of the ball 52. Once this situation develops, the ball 52 fails to fall down and land exactly on the valve seat even when the pump ceases to discharge the fluid. The check valve possibly fails to fulfill the function thereof. The inconvenience caused by the pebble 51 defies solution because the pebble 51 cannot be removed by resuming the operation of the pump.
An object of this invention is to provide a ball check valve which allows a ball to be infallibly seated even when the ball check valve is laid in a horizontal pipe.
A further object of this invention is to provide, with a view to meeting the demand for an integral check valve assembly, a ball check valve of high practical value, which is endowed with a construction such that an air vent function on the primary side is enabled to be added to a check valve without requiring any enlargement of the check valve and the ball check valve is enabled to retain compactness and enjoy exchangeability of the component parts thereof with conventional supplies.
Another object of this invention is to provide a ball which is enabled, even when extraneous matter such as a pebble happens to reach a point of being possibly nipped between the ball and the guiding part in the body, to move under its own weight infallibly to the seating part in the body and prevent the extraneous matter from being engulfed between the ball and the guiding part.
Yet another object of this invention is to provide a pumping apparatus which permits the ball check valve of this invention to be applied even to a conventional manhole.